THIS SNOWPACK SUMMARY EXPIRED ON January 20, 2018 @ 11:10 am
Snowpack Summary published on January 18, 2018 @ 11:10 am
Issued by Ryan Lewthwaite -

bottom line:

(BWRA still closed) Whelp let's try to cultivate this January storm optimism once again. A very windy low pressure system comes our way today into tomorrow & will bring snow to the 6000' elevations & below. Strong winds gusting to 110 mph are possible & white-out conditions are likely, with the biggest effects to the high Sierra crest. Anxiously we lust for powder & an opening for the BWRA, but it's patience away from those urges that will keep you safe. The Avalanche danger will rapidly increase as we see this storm take shape.

Avalanche Character 1: Storm Slab
Storm Slab avalanches release naturally during snow storms and can be triggered for a few days after a storm. They often release at or below the trigger point. They exist throughout the terrain. Avoid them by waiting for the storm snow to stabilize.

Incoming new snow accumulation could be over a foot. This precipitation will collect on a highly variable snowpack that resides in our mountains. Be suspicious of areas where a deeper snowpack exists such as cross-loaded gullies & abrupt terrain changes.

Avalanche Character 2: Wind Slab
Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.

Our storm is coming in with ferrousioucly high winds. Strong sustained winds could average in the 50 mph range with hurricane-like gusts reaching 110 mph! Snow will be transported to places where a deeper pack resides, especially on Northeast through Eastern aspects. Winds will help increase the storm slabs density, making it more prone to propagation.

Avalanche Character 3: Persistent Slab
Persistent Slab avalanches can be triggered days to weeks after the last storm. They often propagate across and beyond terrain features that would otherwise confine Wind and Storm Slab avalanches. In some cases they can be triggered remotely, from low-angle terrain or adjacent slopes. Give yourself a wide safety buffer to address the uncertainty.

Although less reactive lately, due to warm temps & a period devoid of new snow, the persistent slab issue has not fully dissolved. Whumphing & cracking can still be observed in areas where there is a deeper snowpack.  Understanding where these weak layer pockets linger is paramount to having a safe day in the mountains.  

Snowpack Discussion

The structure of persistent slabs still exists within the snowpack but has been subdued by sintering & spring-like weather. The incoming weather system can have an effect on those buried weak layers by adding stress. The area we dug in whumphed upon our travel across it. Our pit revealed multiple crusts & facet layers with a denser base on top of the ground. Tests were relatively inconclusive with irregular fracture plains in weak layers with moderate pressure. Small surface hoar & suspected near surface faceting below a thin sun crust was observed. Winds have scalloped the snow surface & deposits amongst the sedges were peculiar near ridgeline at 10,500'.

recent observations

A tour yesterday provided a resurgence of hope for our dismal season. Dry & wind-effected snow pockets are there,  although it takes a keen eye to discern what is safest to ride. Whumphing on flatter terrain lower amidst trees is still unsettling to those paying attention. 

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 44 deg. F.
Max. temperature in the last 24 hours: 48 deg. F.
Average wind direction during the last 24 hours:
Average wind speed during the last 24 hours: mph
Maximum wind gust in the last 24 hours: mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 55 inches
weather

Yesterday into this  morning we can expect above average temperatures & strong winds. An aggressively windy low pressure system will settle over us this afternoon into Friday with snow showers likely.  Accumulations have been down-graded for totals but white-out conditions will take place.  Higher alpine areas will see the heaviest effects of wind & snowfall. Projections foresee another storm in the mix for the weekend.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Thursday Thursday Night Friday
Weather: Mostly cloudy with 10% chance of precipitation later Snow level 9000' Mostly cloudy with 80% chance of rain turning to snow late Snow level 8000' dropping to 7000' late Mostly cloudy with 60% chance of snow Snow level below 6000'
Temperatures: 42 - 50 deg. F. 22 - 27 deg. F. 26 - 32 deg. F.
Wind direction: South shifting to Southwest Southwest West
Wind speed: 20 to 40 mph; gusts to 70 mph 30 to 45 mph; gusts to 75 mph 15 to 25 mph; gusts 50 decreasing to 40 mph
Expected snowfall: 0 in. 3 - 6 in. 2 - 5 in.
For above 10000 ft.
  Thursday Thursday Night Friday
Weather: Mostly cloudy with 15% chance of precipitation later Snow level 9000' Cloudy with 90% chance of snow Snow level 8000' dropping to 7000' late Mostly cloudy with 75% chance of snow Snow level below 6000'
Temperatures: 35 - 40 deg. F. 17 - 22 deg. F. 20 - 25 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 45 to 60 mph; gusts to 90 mph increasing 50 to 70 mph; gusts to 100 mph later 55 to 75 mph; gusts to 75 mph decreasing 50 to 65 mph; gusts to 110 mph late 30 to 45 mph; gusts to 70 mph Decreasing 20 to 30 mph; gusts to 50 mph later
Expected snowfall: 0 in. 3 - 7 in. 2 - 5 in.
Disclaimer

This snowpack summary applies only to backcountry areas in the Bridgeport Winter Recreation Area. Click here for a map of the area. This snowpack summary describes general avalanche conditions and local variations always occur. This snowpack summary expires in 48 hours unless otherwise noted. The information in this snowpack summary is provided by the USDA Forest Service who is solely responsible for its content.